Questions: Phonological Development and Speech Sound Acquisition

Question 1

A 6-month-old Japanese infant and an 18-month-old Japanese infant are both tested on their ability to discriminate English /r/ from /l/. What result does phonological development research predict?

• A. The 18-month-old performs better, because more language experience improves all phoneme discriminations
• B. Both perform equally well, since this is a universal human auditory capacity
• C. The 6-month-old performs better, because perceptual narrowing has not yet occurred
• D. The 18-month-old performs better only if exposed to English in the home

Answer: (C)

Perceptual narrowing during the first year tunes infants' speech perception to their native language's phoneme categories. Japanese infants are initially capable of discriminating /r/ from /l/ (a distinction Japanese does not contrast), but this ability declines by ~12 months as their perceptual system commits to native-language categories. The 6-month-old, whose system has not yet narrowed, outperforms the 18-month-old on non-native contrasts. Option A reflects the common misconception that all language skills grow monotonically with experience.

Question 2

Canonical babbling (repeated syllables like 'ba-ba-ba') is developmentally significant primarily because it:

• A. Demonstrates that the infant has mastered the phoneme inventory of the native language
• B. Reflects motor learning of the rhythmic jaw and lip movements underlying syllable production
• C. Shows the infant is imitating adult speech patterns heard in the environment
• D. Indicates that the critical period for phonological development has closed

Answer: (B)

Canonical babbling, which emerges around 6–10 months, is significant as motor learning, not phoneme mastery. The infant is practicing the repetitive articulatory cycles — jaw movement, lip closure — that form the basis of syllable production. Evidence: deaf infants with sufficient early auditory input begin canonical babbling on schedule, while those with severe hearing loss do not, showing that acoustic feedback drives this motor learning process. The phoneme inventory is far from mastered at this stage.

Question 3

When a toddler says 'wabbit' instead of 'rabbit,' it is evidence that they have not yet perceived the correct adult pronunciation of the word.

• T. True
• F. False

Answer: False

This is a classic misconception. In phonological development, perception *leads* production by several months. The child has almost certainly perceived the adult form correctly — they know 'rabbit' has an /r/. The error reflects a production constraint: the articulatory motor program for /r/ exceeds the child's current motor capacity, so they substitute an easier sound. The production system simply has not caught up to the perceptual system. This distinction between perception and production failure is important for understanding language development and for clinical assessment.

Question 4

Deaf infants who receive sufficient auditory input before the canonical babbling window begin that stage on the same developmental schedule as hearing infants.

• T. True
• F. False

Answer: True

This is true and reveals how acoustic feedback drives the motor learning of canonical babbling. Infants with severe hearing loss who do not receive auditory input (through hearing aids or cochlear implants) during the critical window do not begin canonical babbling on schedule — their production timeline is delayed. When adequate input is restored early enough, development proceeds normally. This demonstrates that babbling is not purely internally driven motor maturation but requires auditory feedback to proceed.

Question 5

Explain why the decline in non-native phoneme discrimination that occurs in the first year of life represents a developmental gain, not a loss.

Model answer: The decline reflects perceptual specialization, not degradation. By committing to the phoneme categories of the native language, the infant's system becomes faster and more precise at the distinctions that actually matter for understanding speech in their environment. A Japanese speaker does not need to discriminate /r/ from /l/ — those are allophones of the same phoneme in Japanese. The broad initial sensitivity is a preparatory state; the narrowing is the acquisition of a working perceptual grammar. The infant trades universal sensitivity for native-language fluency.

This is the core insight of the sensitive-period framework applied to phonology. The initial universal sensitivity is not a skill to be preserved but a scaffold for building a language-specific system. Perceptual narrowing is the output of successful learning from the statistical distribution of sounds in the ambient language. Treating it as loss misunderstands development as accumulation; phonological development is more like carving — structure is achieved by selectively discarding what is not needed.